Cleaning solutions containing a salt such as an alkanolamine salt of a C.sub.6 -C.sub.12 branched or straight chain aliphatic carboxylic acid, a nonionic surfactant, and a surface-active quaternary ammonium compound are known to the art for degreasing and cleaning metal parts while at the same time protecting the metal parts against corrosion. Such compositions are disclosed, for example, in U.S. Pat. No. 4,284,434, issued Aug. 18, 1981 to Herbert Lingmann, Herman Drosdziok, and Rudolf Peifer and assigned to Henkel Kommanditgesellschaft auf Aktien. These compositions have many commercial uses, including use in automotive assembly lines, where automotive body and other metal components must be cleaned of metal fines and the lubricating oils which are used during their manufacture and assembly.
One of the most difficult problems in cleaning automotive bodies prior to the finishing steps leading to the application of automotive paint is in the removal of unwanted sealants commonly used in sealing and waterproofing joints and openings between metal parts. When such sealants are used, usually by means of extrusion through grease guns, excess quantities of sealant frequently are extruded or dripped onto the adjacent metal parts, and such excess must be removed from the metal before the application of a conversion coating prior to painting. The only known practical method of removing such unwanted sealants is by the use of kerosene. However, kerosene has many disadvantages, including toxicity to the workers using it on prolonged exposure; flammability problems; unpleasant odor; the necessity for repeated applications of the kerosene to heavy accumulations of sealant, since the sealant is not that readily soluble in the kerosene; and the problem of removing excess kerosene from the metal parts, since kerosene has low water solubility and cannot be readily removed by use of a water rinse. In fact, when automotive bodies containing areas coated with kerosene are immersed one after the other in a standard cleaning solution prior to the application of a conversion coating to the metal bodies, the bath relatively rapidly becomes contaminated and rendered ineffective by the kerosene, requiring frequent down time and expense in draining the kerosene contaminated bath and making up a fresh bath.
Heretofore the above disadvantages of kerosene use had to be tolerated since no commercially alternative method of removing contaminating sealants was known.